At issue is a recent revision in the FDA's regulations that allows gay and bisexual men to give blood, but only if they have haven't had sex for a year. (They were previously barred entirely, based on concerns about exposure to HIV.)

With tongue firmly in cheek, Cumming introduces a series of eight nonsexual activities that are "guaranteed to make your year without sex fly by."

Among them: Apply your manual dexterity to packing powder into a Civil War musket; thrust your hips into yoga; and polish your trophies. The "Celibacy Challenge" logo also is a riot—a white lock on a pair of red briefs.

Saatchi and Bullit director Ari Sandel created the mock PSA for Glaad and the Gay Men's Health Crisis, which want the FDA rules to be based on risk factors, not sexual orientation, and are petitioning the federal agency to make that change. The pro-bono ad, which is being distributed online via the hashtag #CelibacyChallenge, went up Thursday on YouTube.